1. Field of the Invention
The present invention generally relates to plaster formulations, and more particularly relates to plaster formulations for mixing color and applying it to the interior walls of houses.
2. Background Information
The present plaster formulations, which are commercially available, have several deficiencies. When applied to the interior walls of houses, current plaster formulations are typically too shinny. People would prefer a plaster that is less shinny. The current formulations scratch too easily, which is undesirable for the workman preparing the surface and also for the homeowner. The biggest problem with current formulations is that all work with the web plaster must be done fairly quickly, because the plaster sets within about forty minutes. What would be preferable is to have more time in which to apply different layers of plaster with different colors. The different layers with different shades of colors result in an attractive effect on the wall.
Another problem with current formulations of plaster, is that they may contain chemicals that are undesirable in a home. More and more people are becoming allergic to various chemicals in the environment. It would be very desirable to have a plaster that did not contain strong fumes, acidic fumes, and in which glues of various types or complex chemicals are not utilized.
These and other objects are accomplished by the plaster formulation of the invention. The plaster formulation of the invention utilizes Keene""s cement as one of its ingredients. J. D. Greenwood and R. W. Keene patented Keene""s cement in 1838. It is a type of interior wall plaster that is obtained primarily from gypsum, which is heated above 170xc2x0 C. to form a hydrous calcium sulfate. This is soaked in a solution of alum (potassium aluminum sulfate) to accelerate the set. The mixture is then reheated to 400xc2x0-500xc2x0 C. and ground to form a plaster.
Mixed with Keene""s cement is crystalline silica. Other ingredients include dolomitic hydrated lime and calcium carbonate. These are mixed together with water to form plaster.
A cement that is considered to be equivalent to Keene""s cement, for the purpose of this formula, is Parian cement. J. Keating patented Parian cement in 1846. As is Keene""s cement, Parian cement is a hard finish plaster. It is prepared in a manner similar to Keene""s cement, except borax is used as an additive to finely powdered gypsum in place of the alum, which is used in Keene""s cement. To make Parian cement, Plaster of Paris is soaked in a solution of borax (sodium borate), cream of tarter (potassium hydrogen tartrate), and in water and subsequently calcined. Synonyms for Parian cement are gypsum cement and hard finish plaster. Although, the formula for the plaster of the invention specifies Keene""s cement, it is intended that that term cover both Keene""s and Parian cement.